Origanum vulgare and Cinnamomum zeylanicum Essential Oils Enhance Disease Resistance to LCDV in Gilthead Seabream (Sparus aurata L.)

The lymphocystis disease virus (LCDV) is a widespread disease in Mediterranean aquaculture and could lead to losses in fry as well as prevent the sale of adult gilthead seabream (Sparus aurata), affecting both hatchery and on-growing stages. Although LCDV infections are often considered self-limiting, they can lead to severe outcomes due to skin microbiome alterations that promote secondary infections, while also reducing growth and marketability, causing substantial economic losses. Basic biosecurity measures are not successful, and there is no available commercial vaccine. This study evaluated diets supplemented with Origanum vulgare and Cinnamomum zeylanicum essential oils (1% and 2%) in gilthead seabream experimentally infected with LCDV. Preventive feeding (90 days before infection) and therapeutic feeding (initiated at infection) were compared across 11 experimental groups, including infected, recovered, and control groups. Results showed that essential oils were more effective prophylactically than therapeutically, highlighting their protective role when incorporated into diets. Cinnamon-supplemented groups consistently exhibited lower prevalence and mortality than oregano groups. High DNA damage values linked to reduced mortality, particularly in the CIN90.1 group, demonstrated that viral dissemination was most restricted. In conclusion, essential oils modulated LCD progression by influencing viral interactions with DNA damage repair mechanisms, supporting their potential for disease control in intensive aquaculture.